Literature from ultrasonic equipment manufacturers advertises the equipment as being used for ultrasonic cleaning of surfaces, usually the removal of soil from the surface. Ultrasonics has also been adapted to a broad range of material removal. For example, it has been disclosed to use ultrasonics to strip a photo-hardened (exposed) resist image from a printed circuit board but no commercial use of ultrasonics for this purpose is known. Instead, stripping has been commercially carried out by solvent treatment only, to dissolve or swell the resist image and thereby remove it from the board surface.
As disclosed in U.S. Pat. No. 3,751,164, it is also known to accelerate the removal of an unexposed area of a photocurable layer to form a relief printing plate. This patent also discloses some degree of automation, involving an overhead rail system for processing the plate in a frame from operation-to-operation including ultrasonic cleaning and rinsing in separate containers. The need exists for compact transport systems in general and in particular for ultrasonic material removal, coupled with better control in critical operations such as stripping of a resist image from a printed circuit. In such stripping operation, it becomes difficult to entirely strip the resist image without stripping away some of the fine circuit lines of the printed circuit.